A coronavirus is an RNA virus with which humans, pigs, cow, chickens and the like are infected. In humans, the coronavirus has been long known as a causal virus of a cold along with an influenza virus. However, the coronavirus and the influenza virus are different in the following points.
That is, the coronavirus is a single-stranded plus chain RNA virus, while the influenza virus is a single-stranded minus chain RNA virus [refer to J. Virol., 29, 293-300 (1979), Am. J. Vet. Res., 37, 1031-41 (1976) and Virus, vol. 52, pp. 55-59, 2002]. Sialic acid molecular types of receptors that influenza viruses A and B and the coronavirus recognize are different [refer to J. Virol., 65, 6232-6273 (1991) and Virology, 189, 121-31 (1992)].
In case of the influenza virus, it has been reported that a host range is changed by substitution of one base of hemagglutinin (HA), one of spike sugar proteins present in a membrane, and it has been further known that attack from a host is escaped by changing an antigen via stimulation of an antibody pressure or the like (refer to Virus, vol. 51, pp. 193-200, 2001). Meanwhile, in case of the coronavirus, it has been considered that mutation easily occurs owing to a transcription process of a viral RNA described below.
The transcription processes of viral RNAs of the influenza virus and the coronavirus are different in the following points. Transcription of the viral RNA of the influenza virus takes place in a nucleus of a host cell, and the viral RNA synthesizes a viral template RNA by adding CAP present in a 5′-terminal region of an mRNA of the host cell to a 3′-terminal region of its own, like a primer [refer to J. Gen. Virol., 83, 723-34 (2002)]. Accordingly, it has been clarified that in the influenza virus, the mRNA synthesis on the host side is blocked with an inhibitor of an RNA polymerase such as actinomycin D or α-amanitinto inhibit its growth [refer to Philos Trans R. Soc. Lond. B Biol. Sci., 288, 359-70 (1980) and Arch. Virol., 141, 1587-94 (1996)].
On the other hand, transcription of the coronavirus takes place in a cytoplasm of a host cell. The detail of its process is unknown at present. However, it has been known that at least transcription using an mRNA of a host does not take place. Therefore, transcription is not inhibited, in most cases, with a drug such as actinomycin D or α-amanitin [Refer to Advances in virus research, 48, 1-100 (1997)].
Severe acute respiratory syndrome (hereinafter abbreviated as SARS) virus is a new coronavirus considered to be derived from wild animals. With respect to the number of patients of SARS induced by SARS virus, the number of infected persons in the whole world exceeds 8,439, and the number of the dead is 812 (as of Jul. 3, 2003). Thus, the mortality is high, and the countermeasure for treating or preventing the same is a global urgent necessity. It has been known that SARS virus can be destroyed with an bactericide or a disinfectant such as 75% alcohol. However, drugs effective for prevention or treatment of infection, including vaccines, have been unknown.
Glutathione is a tripeptide having a structure of γ-L-Glu-L-Cys-Gly, and it has been known as a therapeutic agent of acetonemia caused by an alcohol.
Glutathione has been known to have an effect for preventing or treating infectious diseases of the influenza virus which is different from the coronavirus in drug sensitivity (pamphlet of WO 98/30228). However, it has been unknown that glutathione has an effect for preventing or treating infectious diseases of the coronavirus.
Catechin is a water-soluble polyhydric phenol contained in a woody plant in large quantities, and it has been known to have a growth inhibitory activity of the influenza virus [refer to Planta medica, 67, 240-43 (2001)].
Anti-influenza nutrient foods containing glutathione and catechin have been also known (refer to JP-T-2001-511770 (the term “JP-T” as used herein means a published Japanese translation of a PCT patent application)). However, it has been unknown that a catechin-containing composition has an effect for preventing or treating coronavirus infectious diseases.
As a virus belonging to the Flavivirus family which is a single-stranded plus RNA virus, hog cholera virus (CSFV), bovine viral diarrhea virus (BVDV) and the like have been known. Especially BVDV is a virus which involves a serious problem in livestock industry as a virus that induces a hemorrhagic syndrome of high lethality with reduction of platelets. Nevertheless, an effective method for preventing BVDV infectious diseases has been unknown.